1. Field of the Invention
The invention relates to a piston rod-less pneumatic cylinder, that includes a piston longitudinally movable inside a cylinder tube and a transmission element that engages with this piston and projects out through a longitudinal slot in the cylinder tube, along with a sealing tape that seals the longitudinal slot from the inside on either side of the piston, which is routed through the piston in the area of the transmission element, and includes a sealing strip that interacts with two longitudinally-extending sealing areas near the end of the longitudinal slot inside the cylinder, along with at least one fixing strip arranged on the outside of the sealing strip with two fixing elements that lie opposite one another relative to the center plane of the longitudinal slot, and are essentially longitudinally extended and directed toward the outside.
Pneumatic cylinders of the above kind are mostly pneumatically actuated and, due to their piston rodless design, have come to be preferred for use in areas where small fitting length is important. The force exerted on the piston by the pressure medium is conveyed from the transmission element that engages with the piston and projects out through the lateral longitudinal slot to the device to be operated. The delivery chambers lying on either side of the piston are sealed off by packing rings or the like on the piston, and also by the sealing tape covering the longitudinal slot, which is routed toward the inside under the transmission element in the unpressurized area between the piston seals.
2. The Prior Art
The operating pressure prevailing in the respective delivery chamber during actuation of the pneumatic cylinder presses the sealing tape from the inside against the two longitudinally extended sealing areas in the area of the end of the longitudinal slot inside the cylinder, forming a seal. In an unpressurized state, however, precautions must in most instances be taken to prevent the sealing tape from sagging into the cylinder, since at least a temporary leak will otherwise arise during pressurization with the pressure medium. For this reason, one design for a pressure cylinder of the kind mentioned at the outset, e.g., as known from EP 82 829 B1, provides for outwardly directed, longitudinally-extended fixing elements that flexibly press outwardly against the side walls of the longitudinal slot, thereby using clamping and friction forces to bring about a non-positive fit of the sealing tape in the longitudinal slot. EP 147 803 B1 also discloses a similar design, in which the central area of the side walls of the longitudinal slot exhibits rebounding recesses that are expanded relative to accompanying longitudinally extended, projecting fixing lips on the fixing strip of the sealing tape. As a result, the sealing tape is here finally held in a non-positive manner in the longitudinal slot of the cylinder tube by clamping and frictional forces.
In both mentioned known arrangements, in particular in applications involving exposure to strong vibrations or the like, for example, there is a danger that the sealing tape on the unpressurized side will still sag into the cylinder, as a result of which the described initial leaks can become noticeable in a correspondingly disruptive fashion during pressurization. The object of this invention is to avoid the mentioned disadvantages to known arrangements, in particular to design a pneumatic cylinder of the kind discussed at the outset in such a way as to ensure that the sealing tape will hold better in the longitudinal slot using simple means, even in an unpressurized state.